Incorrect mtu set for L2TP interfaces

L2TP related questions
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tj-19
Posts: 36
Joined: 10 Jun 2019, 20:42

Incorrect mtu set for L2TP interfaces

Post by tj-19 »

Hi,

I've got the following set under ppp:-

min-mtu=1280
mtu=1500
mru=1500

I can't see such a setting under L2TP.

When the L2TP tunnels establish, ifconfig l2tp00 etc. shows the mtu is 1420. The CPE connecting is set to 1500 and the path should allow 1500.

if I type ifconfig l2tp00 mtu 1500, this will force the mtu to 1500.

Why is the mtu only 1420?
dimka88
Posts: 866
Joined: 13 Oct 2014, 05:51
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Re: Incorrect mtu set for L2TP interfaces

Post by dimka88 »

Hi tj-19, check docs

[l2tp] has 1420 as mtu by default
ppp-max-mtu=n
By default ppp-max-mtu=1420

Set the maximum MTU value that can be negotiated for PPP over L2TP sessions.
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